KR100762957B1 - Method and apparatus for descrambling AV stream - Google Patents

Abstract

The present invention relates to a method and apparatus for descrambling an audio visual (AV) stream deformed due to scramble, and the first descrambling method according to the present invention provides a method of deforming a stream deformed due to scramble. Obtaining position information of the second descramble information for correcting the second deformed portion of the stream from the first descrambled information for correcting the deformed portion, and descrambles the first deformed portion based on the first descramble information. Quickly find the exact location of the PMT packet containing the obfuscation correction table from the AV stream.

Description

A method and apparatus for descrambling a stream of Ava (Method and apparatus for descrambling AV stream)

1 is a block diagram of a first player according to a conventional first descramble method.

2 is a structural diagram of a calibration table according to a conventional first descramble method.

3 is a structural diagram of a calibration entry according to a conventional first descramble method.

FIG. 4 is a diagram illustrating a descramble operation according to a first descramble method.

5 is a diagram illustrating a problem of a conventional first descramble method.

6 is a configuration diagram of a second player according to a conventional second descramble method.

7 is a structural diagram of a calibration table according to a conventional second descramble method.

8 is a structural diagram of a FUT block according to a conventional second descramble method.

9 is a block diagram of a first player according to an embodiment of the present invention.

10 is a structural diagram of a calibration entry according to one preferred embodiment of the present invention.

11 illustrates a descramble operation according to an embodiment of the present invention.

12 is a block diagram of a second player according to an embodiment of the present invention.

13 is a structural diagram of a FUT block according to an embodiment of the present invention.

14-15 are flowcharts of a first content restoration method according to an embodiment of the present invention.

16-17 are flowcharts of a second content restoration method according to an embodiment of the present invention.

The present invention relates to a method and apparatus for restoring AV content from an AV (Audio Visual) stream stored in a disc, and more particularly, to a method and apparatus for descrambled an AV stream modified due to scramble.

The Advanced Access Content System (AACS) standard, the next-generation optical disc protection system, applies the Broadcast Encryption Scheme to allow players with device key sets revoked due to hacker attacks. Encrypted content cannot be decrypted. The broadcast encryption method assigns a different device key set to each of a plurality of players, and does not store the intermediate key value encrypted with the discarded device key set on a disk distributed in public. The player having the game cannot acquire this intermediate key value, and as a result, cannot obtain the content decryption key.

However, since the number of device key sets is limited, and the number of players to which the device key set should be allocated continues to increase, there is a case where the same device key set is assigned to multiple players. If any one of these players is hacked and the device key set of this player is exposed, there is a problem that other players with the same device key set should also be discarded.

In order to solve this problem, a scramble-based renewability scheme has emerged. This method scrambles in the middle of the content when storing the content on disk, and encrypts it according to the AACS standard. Therefore, in order to restore the original content, the player must also decode the stream stored in the disc according to the AACS standard, and then unscramble the middle of the content.

According to this method, content code, which serves to solve scramble, is stored on the disk. This content code is executed before the content is played back to determine whether there is a problem with the content being played. For example, it is determined whether the player has exposed the device key set, whether illegal copies of the content are running, and the like. As a result, descramble is performed only when it is determined that there is no problem in content reproduction, and descramble is not performed when it is determined that there is a problem. In other words, once the player is sold, it is difficult to update it again, but in the case of a disc, the content level can be updated by inserting the content code as described above for each disc. Conventional schemes for such descramble include the following two examples.

1 is a block diagram of a first player according to a conventional first descramble method.

Referring to FIG. 1, a first player 2 according to a conventional first descramble includes a track buffer 21, a decrypter 22, a buffer 23, and a demux. (24), decoder (25), content code (virtual machine) 26 for protecting AV content included in AV stream, player information database (27), SP register (28), arithmetic unit (29) ), And an overwrite unit 30.

The track buffer 21 reads out the AV stream from the disc 1 and temporarily stores the AV stream in order to correspond to the decoding processing speed in the decryption section 22. The AV stream stored in the track buffer 21 is an AV stream in encrypted form.

The decryption unit 22 decrypts the AV stream stored in the track buffer 21 using the title key Kt corresponding to the AV stream stored in the track buffer 21 according to the AACS standard.

The buffer 23 temporarily stores the AV stream decrypted by the decryption unit 22 in order to correspond to the decoding processing speed in the decryption unit 25. The AV stream stored in the buffer 23 is an AV stream that is deformed due to scramble and encoded according to the Moving Picture Experts Group (MPEG) -2 standard.

The demux 24 demuxes the AV stream stored in the buffer 23 according to the MPEG-2 standard to restore encoded AV content and original AV content from the AV stream stored in the buffer 23. Extract the information. In particular, the demux 24 retrieves a Program Map Table (PMT) packet including an obfuscated fix-up table from the AV stream stored in the buffer 23, and extracts the obfuscation correction table from the PMT packet. do.

The calibration table is a table in which descramble information for correcting the deformed portion of the deformed AV stream due to the scramble in the middle of the AV stream is recorded. The obfuscation correction table is an exclusive OR of the values of the correction table and the secret parameter values so that the values of the correction table cannot be easily understood.

2 is a structural diagram of a calibration table according to a conventional first descramble method.

Referring to FIG. 2, the "SP_ID" field indicates an ID of a secret parameter value used for an exclusive logical OR of a calibration table. "FixUpEntry" indicates a calibration entry that contains substantial information for correcting the deformation due to scramble.

3 is a structural diagram of a calibration entry according to a conventional first descramble method.

Referring to Fig. 3, the "type_indicator" field indicates the processing type of the calibration table. That is, the value "00b" of this field indicates that there is no deformation due to scramble, "01b" indicates that there is deformation due to scramble, and "10b" indicates that it is forensic. The "FM_ID_bit_position" field indicates the bit position of the forensic mark eye for forensic marking. The "relative_SPN (Source Packet Number) _1" field indicates a relative packet number from the PMT packet to the first modified packet. The "relative_SPN_2" field indicates a relative packet number from the PMT packet to the second modified packet. The "byte_position_1" field indicates the start byte position of transform data in the first packet. The "byte_position_2" field indicates the start byte position of transform data in the second transform packet. "overwrite_value_1" represents the first value to be overwritten. The "overwrite_value_2" field indicates a second value to be overwritten.

The decoder 25 restores the original AV content by decoding the AV content extracted by the demux 24 according to the MPEG-2 standard.

The content code 26 for protecting the AV content included in the AV stream reads the content code for securing the AV content included in the AV stream stored on the disc 1 from the disc 1, and By executing the content code, a secret parameter value, a secret parameter ID, and a forensic mark ID are generated. In more detail, the content code 26 for protecting the AV content included in the AV stream compares the player information stored in the player information database 27 with the player information obtained as a result of executing the content code. Determines whether the player has exposed the device key set, and as a result generates a secret parameter value, a secret parameter ID, and a forensic mark ID only if it is determined that the player has not exposed the device key set, and exposes the device key set. If it is determined that the player is one player, the secret parameter value, the secret parameter ID, and the forensic mark ID are not generated.

Forensic marks are not involved in the direct protection of AV content like secret parameters, but if the content with forensic marks is played in a compromised player, a mark specific to this player is created on this content. After this content is exposed to the public, the content owner can identify the compromised player by checking the forensic mark on the exposed content.

The SP register 28 stores secret parameter values, secret parameter IDs, and forensic mark IDs generated by the content code 26 for protecting AV content included in the AV stream.

The calculation unit 29 restores the original calibration table by performing an exclusive OR (XOR) on the secret parameter values stored in the SP register 28 and the obfuscation correction table extracted by the demux 24. Since the obfuscation correction table is an exclusive OR operation performed on the secret correction values with respect to the original correction table, the operation unit 29 once again excludes the obfuscation correction table with the same values as the secret parameter values used in the exclusive OR operation. Restore the original calibration table by performing the OR operation.

The overwrite unit 30 overwrites the descrambled value in the deformed position of the packet deformed by the scramble among the data packets stored in the buffer 23 based on the calibration table restored by the operation unit 29. Descrambles the scrambled portion of the data packets stored in < RTI ID = 0.0 >

FIG. 4 is a diagram illustrating a descramble operation according to a first descramble method.

Referring to FIG. 4, the demux 24 searches for a PMT packet including a calibration table descriptor among TS packets constituting the transport stream output from the buffer 23, and outputs an obfuscation correction table in the PMT packet. . The calculation unit 29 restores the original calibration table by exclusive OR of the calibration table and secret parameter values output from the demux 24. The overwrite unit 30 knows the relative positions of the first packet and the second packet deformed due to scrambled from the values of the "relative_SPN_1" field and the "relative_SPN_2" field of the calibration table restored by the calculating unit 29, respectively. And overwrite the descramble values in these locations.

5 is a diagram illustrating a problem of a conventional first descramble method.

Referring to FIG. 5, when the overwrite unit 30 attempts to overwrite a descramble value at a position of a transport stream stored in the buffer 23, the PMT packet, which is the basis of this position calculation, is stored in the buffer 23. Instead, the demux 24 has already been demuxed. As a result, there has been a problem that it is not easy to calculate the position of the modified part of the transport stream stored in the buffer 23. In addition, when the position calculation of the modified part of the transport stream stored in the buffer 23 is not performed quickly, there is a problem that the modified part of the transport stream stored in the buffer 23 may be output as it is. Therefore, a device using a low specification CPU, such as a mobile terminal, cannot handle the descramble in software due to such a speed limitation.

6 is a configuration diagram of a second player according to a conventional second descramble method.

Referring to FIG. 6, the second player 4 according to the conventional second descramble method includes a track buffer 41, a decryption unit 42, a buffer 43, a demux 44, and a decoding unit 45. And a content code 46 for protecting AV content included in the AV stream, a player information database 47, an SP register 48, a memory 49, an operation unit 50, and an overwrite unit 51. do.

The track buffer 41 reads out the AV stream from the disc 3 and temporarily stores this AV stream in order to correspond to the decoding processing speed in the decryption section 42. The AV stream stored in the track buffer 41 is an AV stream in encrypted form.

The decryption section 42 decrypts the AV stream stored in the track buffer 41 using the title key Kt corresponding to the AV stream stored in the track buffer 41 according to the AACS standard.

The buffer 43 temporarily stores the AV stream decrypted by the decryption unit 42 in order to correspond to the decoding processing speed in the decryption unit 45. The AV stream stored in the buffer 43 is modified due to scramble and is an AV stream encoded in the MPEG-2 standard.

The demux 44 demultiplexes the AV stream stored in the buffer 43 according to the MPEG-2 standard to restore the encoded AV content and the original AV content from the AV stream stored in the buffer 43. Extract the information.

The decoder 45 restores the original AV content by decoding the AV content extracted by the demux 44 according to the MPEG-2 standard.

The virtual machine 46 reads the content code for protecting the AV content contained in the AV stream stored in the disk 3 from the disk 3, and executes the content code to generate a secret parameter value, a secret parameter ID, and Generates forensic mark ID.

The virtual machine 46 also reads the obfuscation correction table from the disk 3 and loads it into the memory 49. This is a difference from the first descramble method shown in FIG. That is, while the first descramble method shown in FIG. 1 includes obfuscation correction tables at various positions of the AV stream, the second descramble method shown in FIG. 2 has an obfuscation correction table in a separate area of the disc 3. Are recorded in the form of a file.

7 is a structural diagram of a calibration table according to a conventional second descramble method.

Referring to FIG. 7, the "Number of FUT blocks" field indicates the number of calibration table blocks. The "Start address of FUT blocks" field also indicates the byte offset of each calibration table block counted from the start of the calibration table. The "SP_ID" field also indicates the ID of secret parameter values used to exclusive OR this correction table block. In addition, the "FUT block" field indicates a calibration table block obfuscated by an exclusive OR of the secret parameter value indicated by the secret parameter ID.

8 is a structural diagram of a FUT block according to a conventional second descramble method.

Referring to FIG. 8, the "Number of FixUpEntry" field indicates a correction entry number. The "Base SPN for FixUpEntry" field indicates the absolute packet number on which the relative correction entry values are calculated. In other words, this value indicates the packet number of the PMT packet containing the calibration table. "FixUpEntry" indicates a calibration entry that contains substantial information for correcting the deformation due to scramble.

The structure of the calibration entry according to the conventional second descramble method is the same as that of the calibration entry shown in FIG.

The SP register 48 stores secret parameter values, secret parameter IDs, and forensic mark IDs generated by the virtual machine 46.

The calculation unit 50 restores the original calibration table by exclusive OR of the secret parameter values stored in the SP register 48 and the obfuscation correction table loaded in the memory 49.

The overwrite unit 51 overwrites the buffer 43 by overwriting the descramble value in the modified position of the packet deformed by the scramble among the data packets stored in the buffer 43 based on the calibration table restored by the operation unit 50. Descrambles the scrambled portion of the data packets stored in < RTI ID = 0.0 >

According to the second conventional descrambling method, the entire obfuscation correction table must be loaded into the memory, and while the AV content is played back, simultaneously performing descrambling with the entire obfuscation correction table loaded into the memory is performed in the memory of the player. There was a problem that it could cause a significant load.

An object of the present invention is to provide a method and apparatus for quickly processing a descrambling operation for a scramble in the middle of an AV content and reducing a system load due to descrambling. The present invention also provides a computer-readable recording medium having recorded thereon a program for executing the method on a computer.

The first descramble method according to the present invention for solving the technical problem is a first for correcting the second deformed portion of the stream from the first descramble information for correcting the first deformed portion of the stream deformed due to scramble Obtaining location information of the descramble information; And descrambling the first deformable portion based on the first descramble information.

The first descramble device according to the present invention for solving the other technical problem is the first descramble information for correcting the modified portion of the first packet from the first packet among the packets constituting the modified stream due to scramble Extraction unit for extracting; And obtaining position information of the second descramble information for correcting a deformed portion of a second packet of the packets from the first descramble information extracted by the extracting unit, and calculating the calculated information from the first descramble information. And an overwrite portion for overwriting a descramble value for correcting the modified portion of the first packet at a position of the modified portion of the first packet.

In order to solve the above further technical problem, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above-described first descramble method on a computer.

In accordance with another aspect of the present invention, there is provided a second descramble method according to the present invention. The absolute position information of a packet providing the descramble information is obtained from the descramble information for correcting a deformed portion of a stream deformed due to scramble. Making; Calculating a position of the modified part based on the obtained absolute position information; And overwriting a descramble value for correcting the deformed portion at the calculated position.

According to another aspect of the present invention, there is provided a second descramble device including an extractor configured to extract descramble information for correcting a deformed portion of a stream from a stream deformed due to scramble; And descrambling for acquiring absolute position information of a packet including the descramble information from the descramble information extracted by the extracting unit, and correcting the deformed portion at a position calculated based on the obtained absolute position information. Contains an overwrite section that overwrites a value.

In order to solve the above further technical problem, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above-described second descramble method on a computer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

9 is a block diagram of a first player according to an embodiment of the present invention.

Referring to FIG. 9, the first player 6 according to the present embodiment may include a track buffer 61, a decryption unit 62, a buffer 63, a demux 64, a decryption unit 65, and a virtual machine ( 66, the player information database 67, the SP register 68, the FUT extracting section 69, the calculating section 70, and the overwriting section 71.

The track buffer 61 reads out the AV stream from the disc 5 and temporarily stores this AV stream in order to correspond to the decoding processing speed in the decryption unit 62. The AV stream stored in the track buffer 61 is an AV stream in encrypted form.

The decryption unit 62 decrypts the AV stream stored in the track buffer 61 using the title key Kt corresponding to the AV stream stored in the track buffer 61 according to the AACS standard.

The buffer 63 temporarily stores the AV stream decrypted by the decryption unit 62 in order to correspond to the decoding processing speed in the decryption unit 65. The AV stream stored in the buffer 63 is modified due to scramble and is an AV stream encoded in the MPEG-2 standard.

The demux 64 demuxes the AV stream stored in the buffer 63 according to the MPEG-2 standard to restore the encoded AV content and the original AV content from the AV stream stored in the buffer 63. Extract the information. According to this embodiment, the demux 64 does not extract the obfuscation correction table from the AV stream stored in the buffer 63 unlike the conventional art. This function is in charge of the FUT extraction section 69.

 The decoder 65 restores the original AV content by decoding the AV content extracted by the demux 64 according to the MPEG-2 standard.

The virtual machine 66 reads the content code for protecting the AV content contained in the AV stream stored in the disk 5 from the disk 5, and executes the content code to execute the secret parameter value, the secret parameter ID, and Generates forensic mark ID. More specifically, the virtual machine 66 compares the player information stored in the player information database 67 with the player information obtained as a result of executing the content code to determine whether the player 6 has exposed the device key set. As a result, a secret parameter value, a secret parameter ID, and a forensic mark ID are generated only when it is determined that the player key set is not exposed, and a secret parameter value when it is determined that the device key set is exposed. Do not generate secret parameter IDs, and forensic mark IDs.

The SP register 68 stores secret parameter values, secret parameter IDs, and forensic mark IDs generated by the virtual machine 66.

The FUT extractor 69 retrieves the PMT packet including the obfuscation correction table by parsing the AV stream stored in the buffer 63, and extracts the obfuscation correction table from the PMT packet. The FUT extractor 69 may extract the obfuscation correction table more quickly by performing only the obfuscation correction table extraction. The calibration table is a table in which descramble information for correcting the deformed portion of the deformed AV stream due to the scramble in the middle of the AV stream is recorded. The obfuscation correction table is an exclusive OR of the values of the correction table and the secret parameter values so that the values of the correction table cannot be easily understood.

The FUT extractor 69 includes the relative position information of the next PMT packet including the other obfuscation correction table obtained by the overwrite unit 71, that is, the PMT packet which provides the correction table restored by the operation unit 70; The exact position of the next PMT packet including the other obfuscation table can be quickly found from the AV stream based on the number of packets between the next PMT packets including the other obfuscation table. That is, the FUT extractor 69 includes the obfuscation correction table that is different from the PMT packet in the number of PMT packets provided by the overwrite unit 71 and restored by the operation unit 70. The obfuscation correction table is extracted from the PMT packet at the position corresponding to the sum of the number of packets between the PMT packets.

However, in the present embodiment, once the absolute position information of any one PMT packet including the obfuscation correction table is found, the location of the next PMT packets can be quickly found, but the first PMT including the obfuscation correction table can be found. It is difficult to locate the packet. There are several ways to solve this problem.

According to the Blu-ray Disc (BD) standard, an MPEG-2 transport stream consists of at least one aligned unit, which is grouped into 32 source packets. Encoding and decoding processes are performed in this alignment unit. With this in mind, by putting the first obfuscation table in the first of the packets constituting this sorting unit, the FUT extractor 69 does not need to parse all the PMT packets, and thus the packets constituting this sorting unit. Only the first packet needs to be parsed. Therefore, the amount of parsing in the FUT extraction section 69 is reduced to 1/32. That is, the FUT extractor 69 retrieves the PMT packet including the first obfuscation correction table by parsing the first packet among the packets corresponding to the alignment unit of the AV stream stored in the buffer 63, and from this PMT packet Extract the first obfuscation correction table.

In the header of the MPEG-2 TS packet, a flag indicating whether a PMT packet includes an obfuscation correction table may be provided. The FUT extractor 69 determines whether these packets include an obfuscation correction table by checking the values of flags of packets constituting the AV stream stored in the buffer 63, and based on the determination result, corrects the first obfuscation. The PMT packet containing the table is retrieved and the first obfuscation correction table is extracted from the PMT packet.

The structure of the calibration table used in this embodiment is the same as that of the calibration table shown in FIG. However, the structure of the calibration entry included in this calibration table is different from that of the calibration entry shown in FIG.

10 is a structural diagram of a calibration entry according to one preferred embodiment of the present invention.

Referring to FIG. 10, the calibration entry according to the present embodiment is almost the same as the calibration entry shown in FIG. 3, but the following two items have been added. The "Absolute_SPN" field indicates absolute position information of a PMT packet including a current deobfuscated calibration table. In the present embodiment, the absolute position information of the PMT packet means a packet number indicating the number of packets including the obfuscation correction table in all the packets constituting the AV stream. In addition, the "Next_FUT_Position" field indicates relative position information of the next PMT packet including another obfuscation correction table. In the present embodiment, the relative position information of the PMT packet means the number of packets indicating how many packets the PMT packet including another obfuscation table is separated from the next PMT packet including another obfuscation table.

The operation unit 70 restores the original calibration table by exclusive OR of the secret parameter values stored in the SP register 68 and the obfuscation correction table extracted by the FUT extraction unit 69. Since the obfuscation correction table is an exclusive OR operation performed on secret parameter values with respect to the original correction table, the operation unit 68 once again exclusively sets the obfuscation correction table to the same values as the secret parameter values used in the exclusive OR operation. Restore the original calibration table by performing the OR operation.

The overwrite section 71 obtains the absolute position information of the PMT packet which provided this calibration table from the calibration table restored by the calculating section 70, and provides it to the FUT extraction section 69. The overwrite unit 71 can easily find the exact location of the modified packet due to the scramble based on the absolute position information of the PMT packet thus obtained.

In addition, the overwrite unit 71 obtains the relative position information of the next PMT packet including the other obfuscation correction table from the correction table restored by the operation unit 70, and provides this to the FUT extraction unit 69.

In addition, the overwrite unit 71 calculates the position of the modified portion of the modified packet due to the scramble based on the absolute position information of the PMT packet thus obtained. In addition, the overwrite section 71 overwrites the descrambling value for correcting the deformed portion of the deformed packet due to the scrambled position so that the scrambled in the middle of the AV stream is released.

11 illustrates a descramble operation according to an embodiment of the present invention.

Referring to FIG. 11, the FUT extractor 69 retrieves a PMT packet including an obfuscation correction table by parsing an AV stream stored in the buffer 63, and extracts an obfuscation correction table from the PMT packet. Subsequently, the operation unit 70 restores the original calibration table by performing exclusive OR on the secret parameter values stored in the SP register 68 and the obfuscation correction table extracted by the FUT extraction unit 69. Subsequently, the overwriting unit 71 obtains the absolute position information of the PMT packet, that is, the number of the PMT packet, from the calibration table restored by the operation unit 70.

Subsequently, the overwrite unit 71 determines the relative position information of the modified portion of the packet modified due to the scrambled number and number of the PMT packet including the obfuscation correction table from the number of the packet currently being input to the buffer 63, that is, the PMT packet. The position of the deformed portion of the deformed packet due to scramble is calculated by subtracting the sum of the number of packets between the and deformed portions. Packets constituting the AV stream are sequentially input to the buffer 63, and the buffer 63 can know the absolute packet numbers of these packets by counting the packets input to the buffer 63 in order. The buffer 63 provides the overwrite unit 71 with the number of packets currently being input to the buffer 63.

As such, the overwrite unit 71 calculates the position of the deformed portion of the deformed packet due to the scramble based on absolute position information such as the number of the PMT packet including the obfuscation correction table, and thus includes the PMT correction table. It is not necessary to consider how many packets have already exited the buffer 63 and thereafter. That is, the number of packets currently input to the buffer 63 is "Packer Number 2", the number of PMT packets including the obfuscation correction table is "Packet Number 1", and the number of packets between the PMT packets and the modified part is "relative_SPN". In this case, the overwrite unit 71 can easily find the exact location of the deformed packet due to scramble as far back as "Packet Number 2-(Packet Number 1 + relative_SPN)" from the inlet of the buffer 63.

Subsequently, the overwrite section 71 overwrites the descramble value for correcting the deformed portion of the deformed packet due to the scrambled position at the calculated position. The operation in the overwrite unit 71 is repeatedly performed by the number of modified parts of the packet modified by the scramble. In the present embodiment, since the number of modified parts of the packet modified by the scramble is two, it is performed twice.

12 is a block diagram of a second player according to an embodiment of the present invention.

Referring to FIG. 12, the second player 8 according to the present embodiment may include a track buffer 81, a decryption unit 82, a buffer 83, a demux 84, a decryption unit 85, and a virtual machine ( 86, the player information database 87, the SP register 88, the memory 89, the FUT extracting unit 90, the calculating unit 91, and the overwriting unit 92.

The track buffer 81 reads the AV stream from the disc 7 and temporarily stores the AV stream in order to correspond to the decoding processing speed in the decryption unit 82. The AV stream stored in the track buffer 81 is an AV stream in encrypted form.

The decryption unit 82 decrypts the AV stream stored in the track buffer 81 using the title key Kt corresponding to the AV stream stored in the track buffer 81 according to the AACS standard.

The buffer 83 temporarily stores the AV stream decrypted by the decryption unit 82 to correspond to the decoding processing speed in the decryption unit 85. The AV stream stored in the buffer 83 is modified due to scramble and is an AV stream encoded in the MPEG-2 standard.

The demux 84 demultiplexes the AV stream stored in the buffer 83 according to the MPEG-2 standard to restore the encoded AV content and the original AV content from the AV stream stored in the buffer 83. Extract the information.

The decoder 85 restores the original AV content by decoding the AV content extracted by the demux 84 according to the MPEG-2 standard.

The virtual machine 86 reads the content code for protecting the AV title stored in the disc 7 from the disc 7 and executes the content code to generate a secret parameter value, secret parameter ID, and forensic mark ID. do. In addition, the virtual machine 86 reads the obfuscation correction table from the disk 7 and loads it into the memory 89 only when retrieving the first packet including the first obfuscation correction table.

The structure of the abbreviated calibration table used in this embodiment is the same as that of the calibration table shown in FIG. However, the structure of the FUT block included in this abbreviated correction table is different from that of the FUT block shown in FIG.

13 is a structural diagram of a FUT block according to an embodiment of the present invention.

Referring to FIG. 13, in the FUT block according to the present embodiment, the “FixUpEntry” field is removed from the FUT block shown in FIG. 8. According to the present embodiment, since information recorded in the "FixUpEntry" field, which occupies most of the FUT block shown in FIG. 8, can be obtained from an AV stream, the FUT block according to the present embodiment includes a PMT packet including an obfuscation correction table. Only the number "Base SPN for each FixUpEntry" field is left. As a result, the abbreviated calibration table according to the present embodiment is reduced in capacity by 1/5 compared with the original calibration table.

As such, the entire obfuscation table is loaded into the memory by loading the obfuscation correction table, which is much smaller than the original obfuscation table, into the memory 89 only when the PMT packet including the first obfuscation table is retrieved. The burden of running descrambles at the same time can be eliminated.

The SP register 88 stores the secret parameter value, secret parameter ID, and forensic mark ID generated by the virtual machine 86.

The FUT extractor 90 is the absolute position information of the PMT packet including the first obfuscation correction table provided from the overwrite unit 92, that is, the first obfuscation correction table from the PMT packet at the position corresponding to the number of the PMT packet. Extract

In addition, the FUT extractor 90 extracts the obfuscation correction table from the AV stream based on the relative position information of the next PMT packet including another obfuscation correction table provided from the overwriting unit 92 at the number of PMT packets. In more detail, the FUT extractor 90 adds the relative position information of the next PMT packet, that is, the number of packets between PMT packets, including another obfuscation correction table provided from the overwrite unit 92 to the number of PMT packets. The obfuscation table is extracted from the PMT packet corresponding to the value. The FUT extractor 90 may quickly find the PMT packet including the N th obfuscation correction table by repeating the above process.

The operation unit 91 restores the original reduced calibration table by exclusive OR of the secret parameter values stored in the SP register 88 and the obfuscated reduced calibration table loaded in the memory 87. In addition, the operation unit 91 restores the original calibration table by exclusive OR of the secret parameter values stored in the SP register 88 and the obfuscation correction table extracted by the FUT extraction unit 90.

The overwrite unit 92 obtains absolute position information of the PMT packet including the first calibration table from the reduced calibration table restored by the operation unit 91, and provides this to the FUT extraction unit 90.

The overwriting section 92 obtains the absolute position information of the PMT packet which provided this calibration table from the calibration table restored by the calculating section 91. In addition, the overwrite unit 92 obtains the relative position information of the next PMT packet including the other obfuscation correction table from the correction table restored by the operation unit 91, and provides this to the FUT extraction unit 90.

In addition, the overwrite unit 92 calculates the position of the modified portion of the modified packet due to the scramble based on the absolute position information of the PMT packet thus obtained. In addition, the overwrite section 92 overwrites the descramble value for correcting the deformed portion of the deformed packet due to the scrambled position so that the scrambled in the middle of the AV stream is released. In more detail, the overwrite unit 92 may include the relative position information of the modified portion of the modified packet due to the scrambled number of the PMT packet including the obfuscation correction table from the number of the packet currently being input to the buffer 83, In other words, by subtracting the sum of the number of packets between the PMT packet and the modified portion, the position of the modified portion of the modified packet due to scramble is calculated.

14-15 are flowcharts of a first content restoration method according to an embodiment of the present invention.

14-15, the first content restoration method according to the present embodiment includes the following steps. The first content reconstruction method according to the present embodiment consists of steps processed in time series in the first player 6 shown in FIG. Therefore, even if omitted below, the contents described above with respect to the first player 6 shown in FIG. 9 also apply to the first content restoration method according to the present embodiment.

In step 141, the player 6 reads the AV stream from the disc 5, and temporarily stores this AV stream. The stored AV stream in step 141 is an encrypted AV stream.

In step 142, the player 6 decrypts the AV stream stored in step 141 using the title key Kt corresponding to the AV stream stored in step 141 according to the AACS standard.

In step 143, the player 6 temporarily stores the decrypted AV stream in step 142. The AV stream stored in step 143 is modified due to scramble and is an AV stream encoded according to the MPEG-2 standard.

In step 144, the player 6 reads the content code for protecting the AV content contained in the AV stream stored in the disc 5 from the disc 5, and executes the content code to execute the secret parameter value, secret parameter ID. Generate for, and forensic mark IDs.

In step 145 the player 6 stores the secret parameter value, secret parameter ID, and forensic mark ID generated in step 144.

In step 146, the player 6 retrieves the PMT packet including the first obfuscation correction table by parsing the first of the packets corresponding to the sorting unit of the AV stream stored in step 143, and from this PMT packet Extract the obfuscation correction table. In addition, in step 146, the player 6 determines whether these packets include an obfuscation correction table by checking the values of flags of packets constituting the AV stream stored in step 143, and based on the result of the determination, the first obfuscation is performed. The PMT packet containing the calibration table may be retrieved and the first obfuscation correction table may be extracted from the PMT packet.

In step 147 the player 6 restores the original calibration table by exclusive OR of the secret parameter values stored in step 145 and the obfuscation correction table extracted in step 146 or 152.

In step 148 the player 6 obtains the absolute position information of the PMT packet which provided this correction table from the correction table restored in step 147 and the relative position information of the next PMT packet including another obfuscation correction table.

In step 149, the player 6 calculates the position of the deformed portion of the deformed packet due to the scramble based on the absolute position information of the PMT packet obtained in step 148. In more detail, in step 149 the player 6 determines the relative number of the modified portion of the packet deformed due to the scramble of the number of PMT packets including the obfuscation correction table from the number of packets currently being input for storage in step 143. By subtracting the position information, that is, the sum of the number of packets between the PMT packet and the modified portion, the position of the modified portion of the modified packet due to scramble is calculated.

In step 150 the player 6 overwrites the descramble value for correcting the deformed portion of the deformed packet due to the scrambled position in the step 149.

In step 151, the player 6 determines whether the relative position information of the next PMT packet including the obfuscation correction table obtained in step 148 is present, and if the relative position information of the next PMT packet exists as a result of the determination, If the relative position information of the next PMT packet does not exist, the process proceeds to step 153. Determining whether there is relative position information of the next PMT packet including the obfuscation correction table means determining whether all scrambles in the middle of the AV stream have been solved.

In step 152, the player 6 extracts the obfuscation correction table from the AV stream based on the relative position information of the next PMT packet including the obfuscation correction table obtained in step 148, and returns to step 147.

In step 153, the player 6 restores the encoded AV content and the original AV content from the AV stream stored in step 143 by demuxing the AV stream descrambled in steps 144 to 152 according to the MPEG-2 standard. Extract a variety of information for

In step 154, the player 6 restores the original AV content by decoding the AV content extracted in step 153 according to the MPEG-2 standard.

16-17 are flowcharts of a second content restoration method according to an embodiment of the present invention.

16-17, the second content reconstruction method according to the present embodiment includes the following steps. The second content reconstruction method according to the present embodiment consists of steps processed in time series in the second player 8 shown in FIG. Therefore, even if omitted below, the contents described above with respect to the second player 8 shown in FIG. 12 are also applied to the second content restoration method according to the present embodiment.

In step 161, the second player 8 reads out the AV stream from the disc 7 and temporarily stores the AV stream. The AV stream stored in step 161 is an AV stream in encrypted form.

In step 162, the second player 8 decrypts the AV stream stored in the track buffer 81 using the title key Kt corresponding to the AV stream stored in step 161 according to the AACS standard.

In step 163 the second player 8 temporarily stores the decrypted AV stream in step 162. The AV stream stored in step 163 is transformed due to scramble and is an AV stream encoded according to the MPEG-2 standard.

In step 164, the second player 8 reads the content code for protecting the AV title stored on the disc 7 from the disc 7, and executes the content code to execute the secret parameter value, the secret parameter ID, and the forensic expression. Create a mark ID. Further, in step 164, the second player 8 reads the obfuscation correction table from the disc 7 and loads it into the memory 89 only when retrieving the first packet including the first obfuscation correction table.

In step 165, the second player 8 stores the secret parameter value, the secret parameter ID, and the forensic mark ID generated in step 164.

In step 166 the second player 8 restores the original reduced calibration table by exclusive OR of the secret parameter values stored in step 165 and the obfuscated reduced calibration table loaded in the memory 87 in step 164.

In step 167, the second player 8 obtains absolute position information of the PMT packet including the first obfuscation correction table from the reduced correction table restored in step 166.

In operation 168, the second player 8 extracts the first obfuscation correction table from the PMT packet at the position corresponding to the information obtained in operation 167.

In operation 169, the second player 8 restores the original calibration table by exclusive OR of the secret parameter values stored in operation 165 and the obfuscation correction table extracted in operation 167.

In step 170, the second player 8 obtains the absolute position information of the PMT packet which provided this calibration table from the calibration table restored in step 169, and obtains the relative position information of the next PMT packet including another obfuscation correction table. do.

In operation 171, the second player 8 calculates the position of the modified portion of the modified packet due to the scramble based on the absolute position information of the PMT packet obtained in operation 170.

In step 172, the second player 8 overwrites the descramble value for correcting the deformed portion of the deformed packet due to the scramble at the position calculated in step 171.

In step 173, the player 6 determines whether there is relative position information of the next PMT packet including the obfuscation correction table obtained in step 170, and if the relative position information of the next PMT packet exists as a result of the determination, The flow proceeds to step 174, and if there is no relative position information of the next PMT packet, the flow proceeds to step 175.

In step 174, the player 6 extracts the obfuscation correction table from the AV stream based on the relative position information of the next PMT packet including the obfuscation correction table obtained in step 170, and returns to step 169.

In step 175, the player 6 restores the encoded AV content and the original AV content from the AV stream stored in step 163 by demuxing the descrambled AV stream in steps 164 to 174 according to the MPEG-2 standard. Extract a variety of information for

In step 176, the player 6 restores the original AV content by decoding the AV content extracted in step 175 according to the MPEG-2 standard.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium. In addition, the structure of the data used in the above-described embodiment of the present invention can be recorded on the computer-readable recording medium through various means.

The computer-readable recording medium may be a magnetic storage medium (for example, ROM, floppy disk, hard disk, etc.), an optical reading medium (for example, CD-ROM, DVD, etc.) and a carrier wave (for example, the Internet). Storage medium).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to the present invention, obfuscation from an AV stream is obtained by obtaining position information of a PMT packet including an obfuscation correction table for calibrating another modified portion of the stream from a calibration table for correcting the modified portion of the AV stream modified due to scramble. This has the effect of quickly finding the exact location of the PMT packet containing the calibration table.

Further, according to the present invention, the absolute position information of the PMT packet providing the calibration table is obtained from the calibration table for correcting the deformed portion of the deformed stream due to scramble, so that the correct position of the deformed packet due to the scramble can be easily obtained. There is an effect that can be found.

According to the present invention, the entire obfuscation table is loaded into the memory by loading the obfuscation correction table, which is much smaller than the original obfuscation table, into the memory only when the PMT packet including the first obfuscation table is retrieved. Eliminates the burden of concurrent descrambling.

Furthermore, according to the present invention, the speed of the descrambling operation is increased due to the above-described effects and the system load due to the descrambling is reduced, so that a device using a low specification CPU such as a mobile terminal can also process the descramble by software. I can do it.

Claims (18)

(a) obtaining position information of the second descramble information for correcting the second deformed portion of the stream from the first descramble information for correcting the first deformed portion of the stream deformed due to scramble; And and (b) descrambling the first deformed portion based on the first descramble information. The method of claim 1, Extracting the second descramble information from the stream based on the acquired position information of the second descramble information; And And descrambling the second deformable portion based on the second descramble information. The method of claim 1, Extracting the first descramble information from a first packet among packets constituting the stream; The step (a) of claim 1, wherein the relative position information of the second packet including the second descramble information from the extracted first descramble information. The method of claim 3, wherein The relative position information of the second packet is the number of packets indicating how many packets the second packet is from the first packet, And extracting the second descramble information from a packet at a position corresponding to a value obtained by adding the number of packets to the number of the first packet. The method of claim 1, Loading obfuscated position information of a packet including information for correcting a first modified portion of the modified portions of the stream stored in a separate area of the disk into a memory; And Extracting information for correcting the first deformed portion from a packet of a position corresponding to the information restored from the obfuscated position information loaded in the memory, The step (a) of claim 1, wherein the descrambling method, characterized in that to obtain the position information of the packet including information for correcting the second modified part of the modified parts from the extracted information. The method of claim 1, Retrieving a packet including the first descramble information by parsing a first packet among packets constituting a predetermined unit of the stream, and extracting the first descramble information from the retrieved packet. A descrambling method characterized by the above. The method of claim 1, Determining whether the packets contain information for correcting modified portions of the stream by examining a value of a predetermined flag of packets constituting the stream, and including the first descramble information based on the determination result. Retrieving a packet, and extracting the first descramble information from the retrieved packet. The method of claim 1, And the step (b) is descrambled by overwriting a descramble value for calibrating the first deformed portion to a position of the first deformed portion calculated from the first descrambled information. An extraction unit for extracting first descramble information for correcting a modified portion of the first packet from a first packet among packets constituting the modified stream due to scramble; And Obtaining the position information of the second descramble information for correcting the modified part of the second packet among the packets from the first descramble information extracted by the extracting unit, and calculating the first information calculated from the first descramble information; And an overwrite portion for overwriting a descramble value for correcting the modified portion of the first packet at a position of the modified portion of the first packet. The method of claim 9, The extractor extracts the second descramble information from the stream based on the location information of the second descramble information obtained by the overwrite unit, Wherein the overwrite unit overwrites a descrambling value for correcting the deformed portion of the second packet at a position of the deformed portion of the second packet calculated from the extracted second descramble information. . A non-transitory computer-readable recording medium having recorded thereon a program for executing the method of claim 1. (a) obtaining absolute position information of a packet providing the descrambled information from the descrambled information for correcting the deformed portion of the deformed stream due to scrambled; (b) calculating a position of the modified part based on the obtained absolute position information; And (c) overwriting the descramble value for correcting the deformed portion at the calculated position. The method of claim 12, The absolute position information is a descrambling method, characterized in that the packet number indicating the number of packets containing the descramble information in all the packets constituting the stream. The method of claim 13, Storing the stream; In the step (b), the scramble is performed by subtracting the sum of the number of packets including the descramble information, the number of packets including the descramble information, and the number of packets between the modified portions from the number of packets currently being input for the storage. A descrambling method comprising calculating a position of a portion. The method of claim 12, Generating a secret parameter value based on a content code for protecting content included in the stream and an ID of a player on which the descrambling method is performed; And Restoring the descramble information by performing an exclusive OR of the generated secret parameter value and the obfuscated descramble information. And the step (c) overwrites the descrambled information based on the restored descramble information. An extraction unit for extracting descrambling information for correcting the deformed portion of the stream from the deformed stream due to scramble; And A descramble value for acquiring absolute position information of a packet including the descramble information from the descramble information extracted by the extractor and correcting the deformed portion at a position calculated based on the obtained absolute position information. Descrambling device comprising an overwrite unit for overwriting a. The method of claim 16, And wherein the absolute position information is a packet number indicating a number of times a packet including the descramble information is included in all packets constituting the stream. A computer-readable recording medium having recorded thereon a program for executing the method of claim 12 on a computer.

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